1. Field of the Invention
The present invention relates to a writing data creation method and a charged particle beam writing apparatus, and for example, it relates to a writing apparatus in which multi-columns for writing a pattern on a target workpiece are provided.
2. Description of Related Art
A lithography technique that advances microminiaturization of semiconductor devices is an extremely important process only which forms patterns in semiconductor manufacturing processes. In recent years, with high integration of large-scale integrated circuits (LSI), a circuit critical dimension required for semiconductor devices becomes minuter year by year. In order to form a desired circuit pattern on semiconductor devices, there is required a master pattern (also called a mask or a reticle) of high precision. The electron beam writing technique intrinsically has excellent resolution and is used for manufacturing a highly precise master pattern.
FIG. 15 shows a schematic diagram for illustrating operations of a variable-shaped type electron beam (EB) writing apparatus. As shown in the figure, the variable-shaped electron beam writing apparatus, including two aperture plates, operates as follows: A first or “upper” aperture plate 410 has a rectangular opening or “hole” 411 for shaping an electron beam 330. This shape of the rectangular opening may also be a square, a rhombus, a rhomboid, etc. A second or “lower” aperture plate 420 has a variable-shaped opening 421 for shaping the electron beam 330 that passed through the opening 411 into a desired rectangular shape. The electron beam 330 being emitted from a charged particle source 430 and having passed through the opening 411 is deflected by a deflector to penetrate a part of the variable-shaped opening 421 and thereby to irradiate a target workpiece or “sample” mounted on a stage which continuously moves in one predetermined direction (e.g. X direction) during the writing. In other words, a rectangular shape capable of passing through both the opening 411 and the variable-shaped opening 421 is written in the writing region of a target workpiece 340 on the stage. This method of writing or “forming” a given shape by letting beams pass through both the opening 411 and the variable-shaped opening 421 is referred to as a “variable shaping” method.
Conventionally, there is used an electron beam writing apparatus which emits one beam (single beam) from a single column where one optical system column is loaded in one electron lens barrel. In the electron beam writing apparatus using a single beam, an LSI pattern is virtually divided into regions, each of which is called a stripe, a frame or a field, and by writing them in order, the whole LSI pattern is written or “drawn.” In the method of continuously moving the stage on which a mask is placed, the region is called a stripe or a frame. In the method of writing by a step and repeat operation, the region is called a field. The size of the region is determined based on a maximum deflection region of a corresponding deflector, and then, the region is divided according to the size.
On the other hand, compared with the writing apparatus employing the single column system mentioned above, there is developed a writing apparatus employing a multi-column cell (MCC) system where two or more optical system columns are loaded in one electron lens barrel. Each column is structured to have the same writing conditions, and a variable shaping writing is performed in each column respectively. (For example, refer to [1] “Multi-column cell MCC-PoC (proof of concept) system evaluation”, by H. Yasuda, T. Haraguchi, et al., the third Symposium on Charged Particle Optics, pp. 125-128, Sep. 18-19, 2003, [2] “Development of electromagnetic lenses for multielectron beam lithography system”, by T. Haraguchi, T. Sakazaki, S. Hamaguchi and H. Yasuda, 2726, J. Vac. Sci. Technol. (Journal of Vacuum Science and Technology) B20 (6), and November/December 2002, and [3] “Multicolumn cell: Evaluation of the proof of concept system”, by T. Haraguchi, T. Sakazaki, T. Satoh, M. Nakano, S. Hamaguchi, T. Kiuchi, H. Yabara and H. Yasuda, 985, J. Vac. Sci. Technol. B22 (3), May/June 2004.) When the multi-column system is adopted, the region dividing method of the single column system mentioned above cannot be used as it is. This is because the distance between the optical centers of both the columns is unique to the apparatus, and for example, it is fixed to 1.1 cm. Then, the distance does not match with the positional relation of a frame or a stripe. If writing is started and continued in such a state, since there exists a region that overflows from a region where deflection can be performed at stable precision, the writing will be executed, in many cases, while deflection is performed up to a position outside the range of each frame. Thereby, there has been a problem of deterioration of writing precision.
When a multi-column system is adopted, writing data is required for each column. Therefore, the number of times of required operation processing increases, and a calculator for them becomes necessary. Thus, there is also a problem that the apparatus itself will be enlarged. Therefore, miniaturization of the apparatus is required, but conventionally it has not been sufficiently solved yet. Moreover, it is also required to shorten the writing time by adopting the multi-column system, but however concrete methods have not been conventionally proposed yet.
As mentioned above, there is a problem that the region dividing method of the single column system stated above cannot be employed as it is because the distance between the optical centers of each column of a multi-column system does not match with the positional relation of a frame or a stripe. Moreover, in the apparatus of the multi-column system, it is requested to reduce the number of parts, and the volume or the number of times of operation processing. Furthermore, it is requested to shorten the time of writing.